Check valves are self-actuating devices used in fluid handling systems to permit free flow of the fluid in one direction and to prevent flow in the opposite direction. The basic elements of industrial check valves are a sealing member which may be a plate, disk, or poppet, hinged or supported in a valve body so that flow in one direction causes the sealing member to move away from a valve seat while flow in the opposite direction causes the sealing member to move against the valve seat, providing a flow tight seal. Springs may be provided to assist the sealing member to close on flow reversal and to maintain it in firm contact with the valve seat. Damping devices may be installed to prevent the valve from slamming closed when flow is suddenly reversed or chattering in the case of pulsating flow conditions.
Swing check valves in which a hinged sealing member or members are moved out of the fluid path by flow in the preferred direction and move back against a sealing surface when flow stops or reverses find widespread use in applications where cleaning tools or material separators must be passed through the line.
The most common type of swing check valve in general use is the flat plate type, typified by Wheatley, U.S. Pat. No. 3,334,652. A flat plate valve requires, however that a housing be provided for containing the plate when it is swung from the closed position to the open position resulting in a heavy, cumbersome structure when large diameter valves are involved.
A second form of swing check valves employs an arcuate member or members as the sealing elements. In the arcuate check valve the sealing element or elements have the same geometry as that of the fluid passage so that when swung out of the flow path the sealing element or elements lie on the interior wall of the fluid passage. Arcuate check valves may be of the split leaf type as shown in Noll, U.S. Pat. No. 586,618; Pranter, U.S. Pat. No. 2,956,582; Collar, U.S. Pat. No. 3,127,148 and Upham, U.S. Pat. No. 4,209,037 or of the single element type typified by Maslow, U.S. Pat. No. 2,913,001. A disadvantage of these valves, which the present invention seeks to overcome, is that, when closed, they are required to seal on planes both perpendicular and parallel to the direction of reverse fluid flow, complicating the problem of obtaining a leak proof seal.
In a previous application I disclosed an arcuate swing check valve having sealing surfaces developed by making intersecting 45 degree cuts to the axis of a tubular member, producing a valve seat having a 90 degree included angle. While this was an improvement on the prior art it proved difficult to obtain tight sealing at the apex of the seat, a condition which the present application seeks to remedy.
A first objective of this invention is to provide a check valve which, in the open position, has an unobstructed flow passage through the valve permitting the passage through the valve of cleaning tools or material separators.
Another objective of the present invention is to provide a valve which reduces turbulence within the valve to a practical limit, thus reducing pressure drop through the valve.
A further objective of this invention is to provide a check valve which can be simply fabricated from cylindrical sections of pipe or conduit without requiring castings and which significantly reduces the machining required to fabricate a check valve.
Still a further objective of this invention is to provide a check valve which reduces the overall size and weight of a valve to its practical and theoretical minimum.
And yet another objective of the present invention is to use the reverse flow, which closes the valve, to cause self alignment of the sealing member with respect to the valve seat so as to provide positive self alignment of the sealing member on the valve seat.